U.S. patent application number 14/377403 was filed with the patent office on 2017-06-01 for novel material.
The applicant listed for this patent is UNIVERSITY OF LEEDS. Invention is credited to Toney Teddy Fernandez, Peter John Grant, Animesh Jha, Gin Jose, Sikha Saha, David Paul Steenson.
Application Number | 20170152174 14/377403 |
Document ID | / |
Family ID | 45896770 |
Filed Date | 2017-06-01 |
United States Patent
Application |
20170152174 |
Kind Code |
A9 |
Jose; Gin ; et al. |
June 1, 2017 |
NOVEL MATERIAL
Abstract
The present invention relates to a substrate comprising an
ion-implanted layer, for example a cation, wherein the ion
implanted layer has a uniform distribution of the implanted ions at
a significantly greater depth than previously possible. The
invention further comprises said substrate wherein the substrate is
a silicon based substrate, such as glass. The invention also
comprises the use of said material as a waveguide and the use of
said material in measurement devices.
Inventors: |
Jose; Gin; (Leeds,
Yorkshire, GB) ; Fernandez; Toney Teddy; (Kerala,
IN) ; Grant; Peter John; (Leeds, Yorkshire, GB)
; Jha; Animesh; (Leeds, Yorkshire, GB) ; Saha;
Sikha; (Leeds, Yorkshire, GB) ; Steenson; David
Paul; (Bradford, Yorkshire, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UNIVERSITY OF LEEDS |
Leeds, Yorkshire |
|
GB |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20150353419 A1 |
December 10, 2015 |
|
|
Family ID: |
45896770 |
Appl. No.: |
14/377403 |
Filed: |
February 8, 2013 |
PCT Filed: |
February 8, 2013 |
PCT NO: |
PCT/GB2013/050300 PCKC 00 |
371 Date: |
August 7, 2014 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 14/32 20130101;
C23C 14/48 20130101; Y10T 428/315 20150115; C23C 14/28 20130101;
C03C 23/0055 20130101; G02B 2006/12061 20130101; Y10T 428/31
20150115; C03C 3/04 20130101; G02B 2006/12188 20130101; C23C 14/221
20130101; A61B 5/1455 20130101 |
International
Class: |
C03C 23/00 20060101
C03C023/00; C23C 14/48 20060101 C23C014/48; A61B 5/1455 20060101
A61B005/1455; C03C 3/04 20060101 C03C003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 8, 2012 |
GB |
1202128.3 |
Claims
1. A substrate comprising an ion-implanted layer wherein the
penetration depth of the implanted ions is at least 50 nm, or at
least 200 nm.
2. A substrate according to claim 1 where the penetration depth of
the implanted ions is at least 500 nm.
3. A substrate according to claim 1 wherein the ion implanted layer
has a substantially uniform distribution of the implanted ions.
4. A substrate according to claim 1 wherein the ion implanted layer
has an implanted ion density of at least 10.sup.21 ions cm.sup.-3,
or at least 10.sup.23 ions cm.sup.-3.
5. A substrate according to claim 1 wherein the substrate is a
glass selected from silica, silicate, phosphate, tellurite,
tellurite derivatives, germanate, bismuthate and solgel route
glasses.
6. A substrate according to claim 1 wherein the substrate is an
optical polymer.
7. A substrate according to claim 6 wherein the optical polymer is
selected from Poly(methyl methacrylate), polyvinyl alcohol,
polyether ether ketone, polyethylene terephthalate, polyimide,
polypropylene, and polytetrafluoroethylene.
8. A substrate according to claim 1 wherein the ion-implanted layer
is either: (i) on an outside face of the substrate; or (ii) within
the substrate.
9. A substrate according to claim 1 wherein the ion-implanted layer
either: (i) encompasses substantially the whole area of the
substrate; or (ii) comprises one or more zones.
10. A substrate according to claim 9 wherein one or more of the
zones overlap.
11. A substrate according to claim 9 wherein the zones comprise the
same or different ions.
12. A substrate according to claim 1 wherein the ion is a
cation.
13. A substrate according to claim 12 wherein the cation is
selected from the group Nd(3+), Yb(3+), Er(3+), Tm(3+), Pr(3+),
Ho(3+), Sm(3+), Eu(3+), Tb(3+), Ce(3+) and La (3+).
14. A waveguide comprising a substrate according to claim 1.
15. A biosensor comprising a substrate according to claim 1 as an
optical substrate or as a waveguide comprising said substrate.
16. A method for the non-invasive measurement of a metabolite in an
animal which comprises: (i) applying a sensor on or near said
animal, said sensor comprising an optical substrate or waveguide;
(ii) irradiating said substrate or waveguide with a light source
such that a portion of the light escapes into the animal; (iii)
measuring the photoluminescence lifetime of the escaped light;
wherein the recovery lifetime is correlated with the level of the
metabolite.
17. A process for fabricating a substrate according to claim 1
comprising: ablating a target layer with incident radiation from a
laser in the presence of a substrate whereby a quantity of the
target layer is implanted into the substrate.
18. A process according to claim 17 wherein the target layer is
tellurium glass.
19. A process according to claim 17 wherein the laser is a
Femtosecond laser.
20. A process according to claim 17 wherein the substrate is
heated.
21. A substrate comprising an ion-implanted layer wherein the ion
implanted layer has a substantially uniform distribution of the
implanted ions.
22. A substrate comprising an ion-implanted layer wherein the ion
implanted layer has an implanted ion density of at least 10.sup.21
ions cm.sup.-3, or at least 10.sup.23 ions cm.sup.-3.
Description
[0001] The present invention relates to a substrate comprising an
ion-implanted layer, for example a cation, wherein the ion
implanted layer has a uniform distribution of the implanted ions at
a significantly greater depth than previously possible. The
invention further comprises said substrate wherein the substrate is
a silicon based substrate, such as glass. The invention also
comprises the use of said material as a waveguide and the use of
said material in measurement devices.
[0002] Femtosecond pulsed laser plasma deposition (fs-PLD) is a
relatively new technique compared to its nanosecond pulsed
counterpart. Technologically realized in a solid-state device in
mid 90s, the fs-PLD is currently emerging as one of the promising
technology in the field of thin film deposition due to the
employment of femtosecond laser. Depending on the repetition rate
and pulse duration in a fs laser-matter interaction can be tuned to
become either a hot with heat diffusion or, a cold process due to
the lack of heat diffusion process and hence, the laser is used for
the production of plasma plume and energetic ions in several other
techniques such as ion implantation. Recent reports in the fs-PLD
thin films are mainly based on crystalline and semiconductor
materials. At the present time implantation at a scale of only a
few tens of nanometer, otherwise known as sub-plantation, have been
reported. We have found that implantation to a much larger depth is
possible. This observation has the potential to produce new
materials and structures which are otherwise impossible to
fabricate. The unique possibility of implanting ions, such as rare
earth ions opens new realm of photonic devices engineering with
respect to site selective doping by masking, direct printing of
photonic circuits, integrated optical amplifiers in novel
materials, multiple sensors with integrated pump source and data
readouts, possibility of single chip multi-sensor design,
superlattice structures by multi-target deposition.
[0003] International patent application, publication number: WO
2011/030157 describes a method of applying a film to a substrate by
ablating a target with radiation from a laser whereby a quantity of
the target layer is deposited on the substrate. Skelland and
Townsend (1995) Journal of Non-Crystalline Solids 188, 243-253
describes ion-implantation into heated soda-lime glass substrates
whereby the profile of the ions implanted shows a distinct peak
with a gradual drop in ion density either side.
[0004] We have found a process which enables an ion layer to be
implanted into a substrate, such as glass to a much greater depth
than previously possible.
[0005] Thus, according to a first aspect of the invention there is
provided a substrate comprising an ion-implanted layer wherein the
penetration depth of the implanted ions is at least 200 nm, for
example at least 500 nm.
[0006] We have also found that the process provides a uniform
distribution density of the implanted ions in the implanted layer
rather than the density profile showing a peak followed by a drop
off in implanted ion density, in a manner which the ion depths
transcend conventional diffusion and high-energy ion implantation,
due to major structural barriers for ion
diffusion/implantation.
[0007] Thus, according to a further aspect of the invention there
is provided a substrate comprising an ion-implanted layer wherein
the ion implanted layer has a uniform distribution of the implanted
ions.
[0008] We have also found that the process facilitates
ion-implantation to a higher density than prior art processes.
[0009] Thus, according to a further aspect of the invention there
is provided a substrate comprising an ion-implanted layer wherein
the ion implanted layer has an implanted ion density of the order
of 10,000 to several hundred thousands of ppm, depending on the
concentrations of ions in the target material used for fs-laser
ablation. For example, when a target of tellurite glass with 80 mol
% TeO.sub.2-10 mol % ZnO-9 mol % Na.sub.2O and 1 mol %
Er.sub.2O.sub.3 oxide was used to make laser-plasma implantation on
a clean silica surface at 700.degree. C., the implanted ion
concentrations of Te.sup.4+, Na.sup.+, Zn.sup.2+, and Er.sup.3+
correspond to nearly half of the ion concentrations in the bulk
target materials (e.g. 50 ion % Si.sup.4+, 40 ion % Te.sup.4+, 5
ion % of Zn.sup.2+, 4.5 ion % of Na.sup.+, and 0.5 ion % of
Er.sup.3+). These densities are larger than 10.sup.21 ions
cm.sup.-3. In conventional processes, the achievable densities are
an order magnitude less. This specific ability to achieve
remarkably high ion concentrations permits us to engineer bespoke
surfaces which have been unachievable in the past for light guiding
applications. Such an approach also allows us to engineer the
dielectric and spectroscopic properties in the implanted layer. For
example, the implanted layer may be doped with rare-earth ions for
engineering lasers and amplifiers, but also be vertically
integrated with relevant mirrors and photo-active/sensitive
materials, e.g. a metal, polymer, semiconductor, ferro-electric
ceramic for frequency conversion and manipulation, a biological
surface with a protein. A multitude of optically active and passive
functions may be achievable via a combination of chemically
dissimilar materials on to a dielectric surface (glass, polymer and
ceramic).
[0010] According to a further aspect of the invention there is
provided a substrate comprising an ion-implanted layer wherein
[0011] (i) the ion implanted layer has a uniform distribution of
the implanted ions; [0012] (ii) wherein the penetration depth of
the implanted ions is at least 200 nm, for example at least 500
nm.
[0013] According to a further aspect of the invention there is
provided a substrate comprising an ion-implanted layer wherein
[0014] (i) the ion implanted layer has a uniform distribution of
the implanted ions; and [0015] (ii) the implanted ion density is at
least 10.sup.21 ions cm.sup.-3.
[0016] According to a further aspect of the invention there is
provided a substrate comprising an ion-implanted layer wherein
[0017] (i) the penetration depth of the implanted ions is at least
200 nm, for example at least 500 nm; and [0018] (ii) the implanted
ion density is at least 10.sup.21 ions cm.sup.3.
[0019] According to a further aspect of the invention there is
provided a substrate comprising an ion-implanted layer wherein
[0020] (i) the ion implanted layer has a uniform distribution of
the implanted ions; [0021] (ii) wherein the penetration depth of
the implanted ions is at least 200 nm; and [0022] (iii) the
implanted ion density is at least 10.sup.21 ions cm.sup.-3.
[0023] The penetration depth of the ion layer depends on the
substrate used but in general would be at least 250 nm, at least
300 nm, at least 400 nm, at least 500 nm, at least 750 nm, at least
1 .mu.m, at least 1.5 .mu.m, at least 2.0 .mu.m, at least 2.5 .mu.m
and at least 3 .mu.m. In one embodiment the layer has a depth from
about 0 nm to about 3 .mu.m, for example in the range about 0 nm to
about 2.5 .mu.m, about 0 nm to about 2 .mu.m, about 0 nm to about
1.5 .mu.m or about 0 nm to about 1 .mu.m. In a further embodiment
the layer has a depth from about 500 nm to about 3 .mu.m, for
example in the range about 500 nm to about 2.5 .mu.m, about 500 nm
to about 2 .mu.m, about 500 nm to about 1.5 .mu.m or about 500 nm
to about 1 .mu.m.
[0024] In general the implanted ion density is at least
5.times.10.sup.21 ions cm.sup.-3
[0025] The ion implanted layer may comprise one or more ions.
[0026] The implanted layer may be on an outside face of the
substrate or may comprise a layer within the substrate. The
implanted layer may comprise one layer or may comprise two or more
layers with a distinct combination of ion compositions in each
layer. For the avoidance of doubt where there are more than two
layers, two or more non-adjacent layers may have the same ion
composition, for example, to form a sandwich. Multiple dissimilar
materials as targets can be envisaged for tailoring the ion layer
composition.
[0027] The implanted layer can encompass substantially the whole
area of the substrate or can comprise one or more zones. The zones
may comprise distinct areas on or within the substrate or one or
more of the zones may overlap. The zones may comprise the same ion
or ions or one or more of the zones may comprise a different ion or
ions.
[0028] The ion may be a cation.
[0029] The ion may be selected from any cation which is ionisable,
for example one or more of the following groups: [0030] (i) one or
more pre-lanthanide and/or lanthanide ions; [0031] (ii) erbium,
ytterbium, neodymium, praseodymium, holmium, cerium, yttrium,
samarium, europium, gadolinium, terbium, dysprosium or lutetium
ions; [0032] (iii) Nd(3+), Yb(3+), Er(3+), Tm(3+), Pr(3+), Ho(3+),
Sm(3+), Eu(3+), Tb(3+) and Ce(3+), La (3+) ions; [0033] (iv)
tellurium, germanium, zinc, sodium and erbium ions; [0034] (v)
metallic ions: for example, Bi, W, Nb, Ta, Ti, Mo, Cr, Mn, Ga, In,
Sn, Pb [0035] (vi) one or more one or more actinide ions; [0036]
(vii) actinium, americium, berkelium, californium, curium,
einsteinium, fermium, lawrencium, mendelevium, neptunium, nobelium,
plutonium, protactinium, thorium and uranium, [0037] (viii) one or
more transition metals; [0038] (ix) one or more cations selected
from the groups (i) to (ix) above. [0039] (x) One or more anions
which may be of F.sup.-, Cl.sup.-, Br.sup.-, I and chalcogen ions
(S and Se).
[0040] The silicon-based substrate may comprise silicon, glass,
silicon oxide or silicon hydride, siloxane polymer.
[0041] In a further embodiment the silicon-based substrate is
glass. Example of glass include: silica, silicate, phosphate,
tellurite, tellurite derivatives, germanate, bismuthate and solgel
route glasses.
[0042] The polymeric substrate may comprise Poly(methyl
methacrylate) (PMMA), polyvinyl alcohol (PVA), polyether ether
ketone (PEEK), polyethylene terephthalate (PET), polyimide(PI),
polypropylene (PP), and polytetrafluoroethylene (PTFE).
[0043] Novel ion-implanted substrates of the invention have
application in a number of technologies, for example, in
communication, computer or display technology and in laser
assemblies. The novel ion-implanted substrate of the invention may
be used in integrated optics (eg as a signal source), chemical
sensing, environmental sensing, biosensing, micro-nano
spectroscopy, optical communication, micro fluidic devices,
optofluidic devices, terahertz amplifiers, lab-on-chip or optical
tomography.
[0044] The novel ion-implanted substrate of the invention may be
used as a waveguide.
[0045] In one embodiment of the invention there is provided a
waveguide comprising a ion-implanted substrate of the
invention.
[0046] The wavelength range of fluorescence in a chip comprising a
substrate of the invention is governed by the ion which are
implanted into the substrate. The skilled man would be familiar
with the spectral properties of suitable doping ions and therefore
chose the appropriate ions for preparing a ion-implanted substrate
with suitable spectral properties.
[0047] Example of the spectral properties include"
TABLE-US-00001 (i) 1100 nm Yb; (ii) 1530-1580 range Er.sup.3+;
(iii) 1450-1525 and 1725-1900 Thulium; (iv) 1900-2000 nm Ho.sup.3+;
(v) 1750 nm-2200 nm codoping with Tm.sup.3+ and Ho.sup.3+ions; (vi)
1100 nm-2200 nm codoping with Yb.sup.3+, Er.sup.3+, Tm.sup.3+ and
Ho.sup.3+;
[0048] A biosensor system comprising [0049] (i) a laser; [0050]
(ii) a waveguide comprising a substrate of the invention; and
[0051] (iii) a detector.
[0052] A biosensor system comprising [0053] (i) a laser; [0054]
(ii) a photonic chip comprising an ion-implanted substrate of the
invention; and [0055] (iii) a photonic chip integrator.
[0056] When used in waveguides of the invention the substrate may
have a thickness in the range of about 0.1 mm to about 10 mm, such
as in the range of 0.5 mm to about 3 mm.
[0057] In one embodiment the detector is a fast photodiode. In one
embodiment the photodiode is a microsecond photodiode, in a further
embodiment a nanosecond photodiode.
[0058] One use of ion-implanted substrates of the invention is in
the non-invasive detection of metabolites, such as glucose, in
animals, such as in a novel method which measures photoluminescence
lifetime.
[0059] In this method the photoluminescence spectral band of the
dopant(s) overlaps with the characteristic absorption bands in the
1530-2200 nm) of the glucose molecules in the NIR wavelengths. The
measured photoluminescence lifetime of the rare earth ions gets
modified in the glass thin film contained in a photonic sensor due
to the amplification by random scattering and localization of
photoluminescent photons. When a medium containing glucose
interacts with the film, the lifetime modifies as a function of
glucose concentration due to its specific absorption as well as
molecular scattering properties. Thus by an accurate measurement of
the photoluminescence lifetime the concentration of glucose in the
medium can be deduced. Since the absorption and scattering
properties of the photons at different wavelengths within the
emission band varies glucose concentration, the change in the
photoluminescence lifetime at different wavelengths can be used as
an additional feature to enhance the signal due to glucose from
other interferences. This new measurement concept is named as
Spectrally Resolved Photoluminescence Lifetime (SRPL) technique and
is the novel principle of detection that is applied in the photonic
sensor. This new approach avoids the disadvantages of direct
spectroscopic methods such as low sensitivity due to strong signal
absorption and augments the capabilities of Multisensor in
continuous glucose monitoring.
[0060] To describe the principle of the sensor based on lifetime
measurement, the photonic chip and skin can be treated as a
combined scattering medium to because of their characteristically
similar scattering properties. While the skin acts as scattering as
well as absorption medium, gain or amplification of the optical
signal is mainly provided by the doped thin film which is under
laser (980 nm) excitation. The glucose molecules can interact with
the NIR photons generated from the chip in two ways, wavelength
dependent scattering and absorption. Since these molecules are
being dispersed in an inhomogeneous medium like skin, the
scattering by glucose as well as the medium plays an important role
in the photon dynamics. While the scattering by glucose molecules
is incoherent (Rayleigh scattering) and that by skin
inhomogeneities can result in coherent photons. Any measured
increase in the lifetime of the signal photons can be attributed to
it being traveled longer paths in the medium as a result of
increased probability of coherent scattering. In a simple
description this means that the coherent scattering leads to longer
measured lifetime while incoherent scattering by molecules reduces
lifetime of the measured signal as discussed below. Interestingly,
the sensor principle is inherent in the Rayleigh's scattering
law[.sup.i] which states the scattering cross section (a) by
molecules is inversely proportional the fourth power wavelength
(.lamda.) and square of the number of molecules (N) i.e.,
.sigma. .varies. 1 .lamda. 4 N 2 ( 1 ) ##EQU00001##
Thus at a particular wavelength, assuming variations in skin's
physiological parameters are negligible, the larger the number of
glucose molecules lower will be the incoherent scattering cross
section. Hence photons available for coherent scattering increases
leading to an increase in PL lifetime evident from measured
wavelength. FIG. 7 demonstrate this trend slope up to a
concentration of .about.10 mMol/L for three different wavelengths
when a .about.1 .mu.m thick film was used for measurement in blood
samples under controlled conditions. At concentrations higher than
this however the trend reverses and it can attributed increasing
competition between scattering and absorption. Glucose has a flat
absorption response (.about.7.times.10.sup.-5 mM.sup.-1 mm.sup.-1)
within 1534-1580 nm region, therefore at longer wavelengths the
reduction in the scattering cross-section will be at a higher
magnitude due to the 4.sup.th power dependence of .lamda.. At this
context, the light photon-liquid medium interaction operates mainly
on the absorption phenomenon where photons are lost leading to PL
lifetime reduction. This phenomenon generally manifests in large
increase (100's of microseconds) measured lifetime in the
hypoglycaemic region and even upto concentration levels of 10
mMol/l and therefore results in excellent sensitivity.
[0061] In one embodiment of the invention there is provided a
method for the non-invasive measurement of a metabolite in an
animal which comprises: [0062] (i) applying a detector on or near
said animal, for example apply said detector to the skin of the
animal, said detector comprising a wave guide; [0063] (ii)
irradiating said waveguide with a light source, for example, a
laser, such that a portion of the light escapes into the animal;
[0064] (iii) measuring the photoluminescence lifetime of the
escaped light wherein the recovery lifetime is correlated with the
level of the metabolite.
[0065] In a further embodiment the change in the photoluminescence
lifetime at different wavelengths can be used as an additional
feature to enhance the signal due to a metabolite of interest from
other interferences.
[0066] A laser suitable for use in biosensor systems and detection
methods of the invention include a laser in the visible and near
infra red spectrum. For example, a laser with wavelengths in the
near infra red spectrum such as those with wavelengths from about
780 to about 1300 nm, such as in the range about 980 nm to about
1100 nm, for example about 980 nm. In one embodiment the laser is a
tunable continuous wave (cw) random laser within the range of about
1510 to about 1620 nm.
[0067] In one embodiment the power of said laser is in the range 1
mW to 500 mW, such as about 50 mW.
[0068] The light source, for example, a laser can have an angle of
incidence at the waveguide of 1.degree. to 90.degree., for example,
about 45.degree..
[0069] When measuring the recovery lifetime in detection methods of
the invention the light source, for example, a laser is turned on
an off, for example with a frequency of about 1 Hz to about 10
Hz.
[0070] The detection technology of the invention provides wide
detection bandwidth, for example, ranging from 800 to 4000 nm.
[0071] Waveguides suitable for method of non-invasive measurement
of the invention may comprise ion-implanted substrates of the
invention, but would also include any waveguide which facilitates
transmission of light and retrieval of a portion of said light from
a biological material sufficient to measure the recovery
lifetime.
[0072] Metabolites which can be detected by the method of the
invention include: small molecule metabolites, peptides, lipids,
peptides, polypeptides and proteins.
[0073] Small molecules metabolites include: glucose and
lactate.
[0074] The photoluminescence spectral band of the dopant(s)
overlaps with the characteristic absorption bands of the metabolite
or metabolites of interest. For example, in the case of detection
of glucose a spectral band of about 1530 to about 2200 nm) of the
glucose molecules would be acceptable.
[0075] In a further embodiment of the invention there is provided a
process for making a ion-implanted substrate of the invention
comprising:
[0076] ablating a target layer with incident radiation from an
ultrafast laser in the presence of a substrate whereby to implant a
quantity of the target layer in the substrate.
[0077] The process further comprises one or more masks to
facilitate implantation of ions in specific zones of the
substrate.
[0078] The target layer can be any material which when exposed to
incident radiation produces a plasma comprising ions capable of
implanting into the substrate. Examples of target layers include
tellurium glass.
[0079] In one embodiment the target layer is mounted on a
rotational platform.
[0080] The substrate is spaced apart from the target layer, for
example at a distance in the range about 50 mm to 150 mm, for
example a distance of about 70 mm
[0081] The substrate may be heated to facilitate the implantation
of ions into the substrate. The optimum temperature to facilitate
the implantation of ions will depend on the target material used.
In general the optimum temperature is between 0.5 and 0.75 times
the glass transition temperature. In embodiment, when using silica
glass a temperature of about 973K can be used.
[0082] For example, the silica glass transition temperature is
1100-1200.degree. C. Therefore the optimum range is about
550.degree. C.-900.degree. C. (823K-1173K).
[0083] The ultrafast laser may be a attosecond, femtosecond or
picosecond laser. In one embodiment the ultrafast laser is a
femtosecond laser.
[0084] The ultrafast laser may be, for example, a Ti-sapphire
laser, a diode pumped laser such as a Yb-doped or Cr-doped crystal
laser or a fibre laser.
[0085] The laser may be an excimer laser or an exciplex laser.
[0086] The ultrafast laser may be a pulsed laser.
[0087] In the process of the invention, the ultrafast laser may
emit pulses of 15 ps or less for example pulses in the range 1 fs
to 15 ps. In one embodiment in the process of the invention the
ultrafast laser emits pulses of 150 fs or less, for example in the
range about 50 to about 150 fs, for example about 100 fs.
[0088] The pulses may be emitted with a repetition rate in the
range about 400 Hz to about 1 kHz In one embodiment 400 Hz to 800
kHz, for example about 500 kHz.
[0089] The ultrafast laser may be mode-locked.
[0090] The average power of the ultrafast laser may be 80 W or
less.
[0091] The pulse energy is typically in the range 40 to about 80
microjoules, for example about 50 to about 70 microjoules, such as
about 65 microjoules.
[0092] Pulse energy may be selectively adjusted using an
attenuator.
[0093] In one embodiment wavelength is typically about 800 nm,
although a wide range of wavelengths would be suitable.
[0094] The incident radiation may be incident on the target glass
at an angle in the range about 40.degree. to about 80.degree., for
example about 60.degree..
[0095] The process is typically carried out in a vacuum chamber.
The process may be carried out at reduced pressure, for example at
a partial pressure of about 60 mTorr.
[0096] The process may be conducted for example in the presence of
a gas, such as oxygen or in an inert gas.
[0097] The duration of the process may be about 30 minutes or more,
for example about 30 minutes to about 10 hours, such as about 2
hours to about 8 hours. In one embodiment the duration is about 6
hours.
[0098] In a further embodiment of the invention there is provided a
process for making a ion-implanted substrate of the invention
comprising: [0099] (i) providing a target layer; [0100] (ii)
providing s substrate in proximity to said target layer; and [0101]
(iii) directing incident radiation from an ultrafast laser at the
target layer to produce an ion-comprising plasma whereby ions from
said plasma are implanted into the substrate.
[0102] The term `about` when used in this specification refers to a
tolerance of .+-.10%, of the stated value, i.e. about 50%
encompasses any value in the range 45% to 55%, In further
embodiments `about` refers to a tolerance of .+-.5%, .+-.2%,
.+-.1%, .+-.0.5%, .+-.0.2% or 0.1% of the stated value.
[0103] The term `animal` includes mammals, such as humans.
[0104] The term `dopants` refers to ions implanted into a
substrate. Dopants include ions implanted into substrates of the
invention.
[0105] The term `glass` refers to a solid that possesses a
non-crystalline (i.e., amorphous) structure and that exhibits a
glass transition when heated towards the liquid state and which
transmits light in the infrared, visible or ultraviolet spectrum,
i.e. a wavelength of about 10 nM to 300 .mu.m. In one embodiment
`glass` refers to a glass which transmits light in the visible
spectrum i.e. a wavelength of about 380 nm to about 740 nm. In a
further embodiment `glass` refers to a glass which transmits light
in the infrared spectrum i.e. a wavelength of about 740 nm to about
300 .mu.m. In a further embodiment `glass` refers to a glass which
transmits light in the ultraviolet spectrum i.e. a wavelength of
about 10 nm to about 380 nm. In a yet further embodiment `glass`
refers to a glass which transmits light in the wavelength range
about 400 nm to about 2000 nm.
[0106] The term `implantation` refers to ion entering the matrix of
the substrate rather than forming a film on the surface of the
substrate.
[0107] The term `optical polymer` refers to any polymer which
transmits light in the infrared, visible or ultraviolet spectrum,
i.e. a wavelength of about 10 nM to 300 .mu.m. In one embodiment
`optical polymer` refers to a polymer which transmits light in the
visible spectrum i.e. a wavelength of about 380 nm to about 740 nm.
In a further embodiment `optical polymer` refers to a polymer which
transmits light in the infrared spectrum i.e. a wavelength of about
740 nm to about 300 .mu.m. In one embodiment `optical polymer`
refers to a polymer which transmits light in the ultraviolet
spectrum i.e. a wavelength of about 10 nm to about 380 nm. In a yet
further embodiment `optical polymer` refers to optical polymers
which transmits light in the wavelength range about 400 nM to about
2000 nm.
[0108] The term `substrate` refers to a silicon-based substrate or
a polymeric substrate, for example, a material selected from glass
or an optical polymer.
[0109] The term `waveguide` refers to any element which facilitates
transmission of light into a material of interest and facilitates
measurement of light which is retrieved from the material of
interest.
[0110] The invention will now be illustrated with the following
non-limiting examples with reference to the following figures.
[0111] FIG. 1--shows schematically the ablation, plasma production
and the multi-ion diffusion process.
[0112] FIG. 2--shows the SEM and TEM images of the substrate cross
sections with a highly defined and uniformly diffused region in
silica at two different target ablation energies of 47 .mu.J
(Sample A) and 63 .mu.J (Sample B) respectively.
[0113] FIG. 3--shows a 400.times.1600 nm HAADF slices of individual
elements of Sample B.
[0114] FIG. 4 represent the Raman spectrum of ion diffused glass
compared with bare silica and tellurite bulk glass.
[0115] FIG. 5 represents a schematic diagram of a biosensor, such
as a glucose sensor of the invention.
[0116] FIG. 6 shows Molar absorptivity spectra of glucose (solid),
alanine (dashdot-dot), ascorbate (medium dash), lactate (short
dash), urea (dotted), and triacetin (dash-dot) at
37.0.+-.0.1.degree. C. over the first overtone.
[0117] FIG. 7 shows the variation in photoluminescence lifetime
measured at three different wavelengths for human blood sample with
varying concentrations of glucose
ABBREVIATIONS USED
[0118] HAADF high angle angular dark field elemental mapping [0119]
NIR near infra red [0120] SEM Scanning electron microscopy [0121]
TEM Transmission electron microscopy
EXAMPLE 1
Implantation into Silica Glass
[0122] Multi-ion diffusion into silica glass was produced via
femtosecond laser ablation of an erbium doped tellurite glass
target containing zinc and sodium. A Ti-sapphire femtosecond laser
operating at a wavelength of 800 nm with 100 fs pulse width and a
maximum repetition rate of 1 kHz (Coherent Inc, Santa Clara,
Calif., USA) was used to ablate the glass target generating an
expanding plasma plume consisting of multiple metal ions
(multi-ion). A tellurite glass target with a molar composition of
79.5TeO.sub.2: 10ZnO:10Na.sub.2O:0.5Er.sub.2O.sub.3 produces
multiple ions Te4+, Zn2+, Na+ and Er3+, which diffuse into the
silica glass substrate under certain process conditions. The
ablation, plasma production and the multi-ion diffusion process are
schematically shown in FIG. 1.
[0123] Experiments were carried by varying the laser energy,
repetition rate, target to substrate distance and finally the
deposition target temperature. The deposition target was not
translated for the simplicity of the experiment and for a better
understanding of parameter variation along the sample surface.
There was an variation in diffusion depth and refractive index
profile along the surface when radially moving outwards from the
centre, therefore all the characteristic properties of the
modification provided were measured from the centre of the sample
unless otherwise stated.
[0124] Optimum results were obtained for laser energies between 40
.mu.J-75 .mu.J when operated at 500 Hz and 1 kHz. The ablation
target to substrate distance was set at 70 mm and the substrate
temperature was set at 973K. FIG. 2 represents the SEM and TEM
images of the substrate cross sections with a highly defined and
uniformly diffused region in silica at two different target
ablation energies of 47 .mu.J (Sample A) and 63 .mu.J (Sample B)
respectively. Diffusion depths of the ions increased from 350 nm to
850 nm with laser energy while the deposition time was 6 hours and
repetition rate was 500 Hz for both cases. A well-defined boundary
of the diffused and pristine region is clearly visible in the FIG.
2 and the modified region does not show any major clustering of
ions or particle inhomogeneities.
[0125] Further analysis of the diffusion characteristics of each
ions in silica was carried out using high angle angular dark field
(HAADF) elemental mapping of sample B. FIG. 3 depicts a
400.times.1600 nm HAADF slices of individual elements. A line
intensity profile shows the relative concentration profile of each
diffused elements with a well-defined and sharp boundary within the
silica. The oxygen concentration in silica remained unchanged
across the boundary while silicon showed a complementary
concentration profile with respect to the diffused elements. This
indicates the formation of a complex alloy glass of silica with
implanted ions increasing refractive index from 1.457 of that of
silica to 1.626. The atomic concentration of silicon in the
diffused region is determined to be 57% while Te, Zn, Na and Er
constitute the rest in Sample A. This confirms a single step
multi-ion diffusion process in the silica glass substrate. The
diffusion is highly uniform and homogenous along the transverse and
horizontal sections of the silica substrate.
Structural Properties of Diffused Region:
[0126] Silica and tellurite are completely immiscible and will not
form a stable glass under conventional batch melting and quenching
process. However in the results presented above it is demonstrated
that diffusion of metal ions including Te4+ ions in to the silica
glass network is possible. The properties of the implanted silica
glass were measured. No signals of any kind of crystallization were
observed in electron diffraction and XRD characterization proving a
complete amorphous phase of silica-tellurite glass. Raman
spectroscopy was used to analyse the glass network in the diffused
region. FIG. 4 represent the Raman spectrum of ion diffused glass
compared with bare silica and tellurite bulk glass. The TZN bulk
glass shows typical raman spectrum with peaks at 817 cm.sup.-1
(TeO.sub.3+1 and TeO.sub.3 stretching), 653 cm.sup.-1 (TeO.sub.4
stretching) and 520 cm.sup.-1 (Te--O--Te bending). On analysing the
Raman spectrum of the implanted region on the substrate, a broad
peak corresponding to TeO.sub.4 stretching vibrations are found
within the range 600-668 cm.sup.-1. The reduction in intensity is
due to the distortion and destruction of Tea.sub.4 groups. This
observation is supplemented by the fact that the 794 cm.sup.-1
vibration is increased with the formation of more TeO.sub.3+1 and
TeO.sub.3 groups. The 490 cm.sup.-1 peak which is very weak in
silica substrate shows a strong and sharp response in the implanted
glass. This indicates the post-implant state of Si--O--Si bonds,
490 cm.sup.-1 peak in .upsilon.-SiO.sub.2 was experimentally
demonstrated to increase its intensity with elastic tensile stress
and later explained that this is arising from the four-membered
ring structures in .upsilon.-SiO.sub.2. Hence the vibration becomes
stronger when their concentration increases upon increase in
density of .upsilon.-SiO.sub.2. The broadness in the peak found at
600-668 cm.sup.-1 may take up contribution from the reported 604
cm.sup.-1 peak in .upsilon.-SiO.sub.2 due to stretched Si--O bonds
during irradiation process.
* * * * *